Afterload- and preload-dependent interactions in the isolated biventricular working rat heart

Area of Science:

• Cardiovascular Physiology
• Ventricular Mechanics
• Hemodynamics

Background:

• Ventricular interdependence is crucial for cardiac function.
• Understanding interactions between the left ventricle (LV) and right ventricle (RV) is essential for diagnosing and treating heart conditions.

Purpose of the Study:

• To quantify the afterload- (AL) and preload- (PL) dependent interactions between the LV and RV in an isolated biventricular ejecting rat heart.
• To determine the influence of RV activity on LV performance and aortic flow (AF).

Main Methods:

• Measurements of intraventricular pressures (LP(max), RP(max)) and flows (AF, PF) were performed on an isolated rat heart model.
• Left ventricular preload (LVPL) and right ventricular preload (RVPL) were systematically varied across different afterload conditions.

Main Results:

• Systolic interactions showed a significant gain (0.45) between right ventricular peak pressure (RP(max)) and pulmonary flow (PF), with 26% of maximal PF attributable to LV function.
• Reduced RV activity augmented AF by at least 15%.
• RV preload variations influenced AF, with unloading the RV inhibiting AF by 6-37% depending on LV loading conditions.

Conclusions:

• Systolic interactions involve transseptal L-R and paraseptal R-L mechanisms.
• Diastolic interactions are suggested to occur via a unidirectional transseptal R-L mechanism.
• The basal contribution of the RV to LV performance is condition-dependent.